Modeling and optimal management ofsize-structured biological populations

Advanced Systems Analysis (ASA) Program researchers develop and analyze stylized models of biological populations (e.g., fish and forests), in which individuals’ growth significantly depends on their size or age and on the size or age of others. The aim is to understand the consequences of various management strategies and to reveal which management principles can optimize typical economic (e.g., profit) and environmental (e.g., biodiversity) objectives.

Some resources are essentially heterogeneous; biological resources (forests, fish, etc.), for instance, are structured by their size and age. In particular, size/age heterogeneity leads to asymmetric competition between individuals. For example, higher trees shade smaller trees, depriving the latter of some of their sunlight, but not vice versa. Another important heterogeneity is the spatial distribution of a resource. Accounting for heterogeneity in models has a potential to increase the reliability of results; models of optimal control of heterogeneous resources are an important tool for advising to policy on a sustainable exploitation of biological resources.

ASA researchers analyze a fairly generic model of a population of individuals that are heterogeneous in size, in which asymmetric intra-species competition impact vital parameters (growth, mortality, and fertility rates) and decreased the population density disproportionally, favoring bigger individuals. The inflow of newborn individuals is defined by a decreasing-return-to-scale function of the population density. Under these assumptions the existence of a stationary size distribution for any given exploitation rate is proven 


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Last edited: 10 February 2016

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